[PATCH] KVM: PPC: Don't sync timebase when inside KVM

Scott Wood scottwood at freescale.com
Thu Mar 1 06:06:05 EST 2012

On 02/29/2012 12:28 PM, Alexander Graf wrote:
> On 29.02.2012, at 18:50, Scott Wood <scottwood at freescale.com> wrote:
>> On 02/28/2012 08:16 PM, Alexander Graf wrote:
>>> When we know that we're running inside of a KVM guest, we don't have to
>>> worry about synchronizing timebases between different CPUs, since the
>>> host already took care of that.
>>> This fixes CPU overcommit scenarios where vCPUs could hang forever trying
>>> to sync each other while not being scheduled.
>>> Reported-by: Stuart Yoder <B08248 at freescale.com>
>>> Signed-off-by: Alexander Graf <agraf at suse.de>
>> This should apply to any hypervisor, not just KVM.  
> Sure, but do you have a generic function to evaluate that? :)

The presence of a hypervisor node without testing compatible.  Might not
get them all, but at least it will cover more than just KVM.

>> Which platforms are you seeing this on?  If it's on Freescale chips,
>> U-Boot should be doing the sync and Linux should never do it, even in
>> the absence of a hypervisor.
> This is on e500mc.

On e500mc Linux should never by trying to sync the timebase.  If it is,
let's fix that.


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